In this video they mention “crusty sheets”, what do they mean by that? 2:26 https://youtu.be/6LuHS7ZeSjE And at the minute 2:00 when the girl is slang talking she says “sliding in” for messaging, is that slang used often? Because I’ve never heard it before, who do you use it.
For the crusty sheets, they're essentially talking about teens masturbating and locking themselves in their room to prevent people from "walking in on them" during the act. As you can probably guess the "crusty" part is the left over dried residue after they finished.
As for the use of "sliding in" its essentially and old slang word for messaging someone over social media or any other platform to be able to get into a friendship/relationship. Although the popularity of using that slang has since dropped in my opinion and now its more used as a joke.
1) The scene starts by mentioning that the target of the humour has been locked in his bedrom all weekend, and goes on to mention puberty. It is about what horny teenagers do when alone. You can now work out the crusty bed sheets reference for yourself.
2) Sliding in has nothing to do with messaging per se. It is about taking an opportunity to get to know someone you like, by sliding into his life, as opposed to forcing your way into his life.